Taillights are a great part of a car to customize and play with. They're highly visible, distinctive, and everyone has to have them, anyway. I came up with an idea on how to make some extremely dynamic light units for not much more than the cost of some tacky, over-chromed aftermarket ones.

And, even better, it could involve you meeting strangers on Craigslist, which seems to have an inexhaustible supply of cheap, obsolete netbooks. So read on to see how you can make awesome animated taillights that can crash all by themselves!

I had this admittedly goofy idea earlier this week, when there was all the hype around the release of some new shrunken tablet computer. That started me thinking about small computers and their LCD displays, and, just by chance, I had also been thinking about taillights. See where I'm going?

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When I was in Japan, I saw an old Datsun Bluebird SSS that had sequential turn signals and was reminded just how fun a bit of animation at the back of your car can be. That was my first thought about taillights. Later, I was noticing all the cars around that have aftermarket taillight units. Almost always, they're overdone, cheap-looking things, but I understand people's desire to have custom parts for something as noticeable and distinctive as taillights.

I did some research, and found that taillight units— OEM or aftermarket— aren't cheap. They generally range from around $100-$500, depending on the car. Other research revealed that you can find a large number of used netbooks for sale for anywhere from around $100- $150, and almost all of these have full-color LCD displays that are just about the right size to fit in many taillight housings.

So here's the plan: take a pair of old, cheap netbooks, and with some simple software and the right connections, turn them into full-color, animated taillights. There's many other ways to do this, and at first glance, a whole netbook seems like overkill, computing-wise. It is, absolutely. You could do this with an LED array and an Arduino. In fact, many more skilled people than myself have done so. Even my friend Tom Jennings, who's as close to a mechano-electrical genius as I know, attempted to make animated custom taillights for his old AMC Hornet and abandoned the project as too much of a pain.

The key is we can use our society's largesse of computing power to our advantage. By leveraging all the power of these cheap little machines, we can make our job much, much easier.

Here's what we need to do it:

• A pair of cheap netboooks. Really, almost anything will work. You can run Windows or Linux on these. You could use a Mac if you wanted, but unless you have an unwanted Mac laptop laying around, a cheapie netbook is going to be much cheaper. Because cheap. It just needs a working screen and at least one USB port. I prefer a netbook (or, if you have room, a full-sized notebook) over an iOS or Android tablet because it's easier to get software on a netbook, easier to configure for one specific application, and easier to get the custom hardware signals from the car into it. Oh, and it's likely cheaper, too.

• A USB Keyboard encoder: I've used these for other goofy projects; essentially, these are just tools to let you map other external hardware buttons to normal keyboard keys. They're most commonly used for MAME arcade cabinets.

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• Eight automotive relays: These will be used to provide the switch closings that get triggered by the car's existing brake/taillight wiring and get fed into the keyboard encoder. Since the encoder can't take the 12V surge, this will get around that issue as well. We need eight because we have to accomodate four inputs per side: taillight, brake, reverse, and turn indicator.

• A 12V DC to 110 V AC power inverter: You can use a cigarette lighter powered one, but you'll probably want to hard-wire it into a 12V line somewhere in the trunk and mount it out of the way. Its job is to power the two netbooks, which shouldn't draw much power.

• Some sort of housing for the netbooks/screens: This will vary a lot depending on the particular type of car. I'd say the best bet is to find an old used taillight assembly and gut it of bulbs, bulb holders, LEDs, whatever. We want the outer lens (clear is best, but even the colored ones could work if you are willing to give up some image color and clarity) and some of the interior to mount everything. Depending on your skill level, this could be made totally custom out of many materials.

• The software: This is also much easier on a netbook than a tablet. You should be able to do everything you'd need in something like Flash or Processing, both of which are easy enough to learn for something this simple.

Essentially, for your taillight app, you'll need animations for all the main light functions: tail, brake, reverse, and turn. You'll want the dominant colors for your animations to match the legal requirements: red for brake and tail, amber or red for turn (with some blinking or directional animated component) and white for reverse. These can be animated GIFs, Flash SWFs, or whatever.

Your program will have this basic main loop:

• Check for key inputs
• If no input either play idle animation or not, and go back and check again
• If key="B" then play brake animation
• If key="T" then play tail light animation
• If key="L" then play left turn animation
• If key="R" then play right turn animation
• If key="X" then play reverse animation
• Go back to beginning

Of course, the actual keys you use don't matter, really— any will work that are mapped into the keyboard encoder.

The other part of the software step is configuration. You'll need to set up the netbook to execute the full-screen JAVA or SWF or whatever app upon startup, and only run that. You may need to add a "wake up" key to the setup to be able to make sure the netbooks turn on automatically when they get power from the car. There are many ways to handle these parameters under Linux and Windows.

Okay, so here's how this could all fit together:

First, you'll want to take apart the hinge on the netbook, and carefully fold back the bottom so it's behind the screen. I've done this before with laptops to make wall-mount units, and generally, if you're careful with the display's fragile ribbon connector, it works. Different designs may vary, and some even are designed to do this out of the box. Either way, the goal is to make a small, flat package. Use zip ties to hold the unit together.

Remove the existing taillight unit and unplug the wires connecting the bulbs to the housing. We'll need to connect the wires to the pins of our relays. Most cars use one wire for the lights and take the ground from the metal of the car— you may need to run more ground lines. Individual cars will vary. Basically, we want to run the 12V taillight wires to individual relays.

For example, with the brake light wire, we want the 12V that normally would go to illuminate the bulb to trigger the relay closed. The other, output pin of the relay will go into the USB keyboard encoder. The encoder will be connected to the car's ground as well, so the effect of the 12V into the relay and then into the encoder will be the same as pressing a key (closing a switch) on the computer's keyboard. That key will be assigned to the appropriate animation, and boom, working animated tallight.

Make sense? Good. So, repeat this process for all taillight wires, mount the netbook into its housing, and then into the car, repeat for the other side, and then wait for the gender of your choice to start throwing themselves at you.

Or cops. I have no idea if this is illegal, but my guess is as long as you have the proper colors and the screen is bright enough (it's got to be at least as bright as those old 1157 taillight bulbs) you should be okay. I mean, why not? If sequential animated taillights are legal, you'd think these would be, too. Plus, they can be even better, displaying arrows for the turn signals or a big STOP when you're stopping.

To fully disclose, this is just an idea now. I haven't actually tried this one, I just had the idea and thought through a process. So I'd love to hear what you think, and would really, really love it if someone decides to give it a try. I'll absolutely feature you here as a hero if you do.